It's all about storytelling and finding your own voice and own style. For instance, I enjoy writing stories that resemble Firefly episodes. But others write vignettes, or first-person fics, or post-movie fics, or alternate universe fics, or a hundred other styles.

Using Chinese and the other things you asked about, those are all just ingredients in a recipe. You decide what you need and what you don't. The best thing about fanfic is that there are no rules.

Hey, same boat, here. For me, I'm keeping Wash alive for my fic set after the movie. You can really do whatever you want. It's Joss's characters, but your story. Feel free to make a new character! Why not? As for where to start, well, that's up to you. What kind of story do you want to tell? Do you want to focus on a certain mission, or a certain character? I don't think you need to use chinese unless you want to. There are a few easy translations floating around the board here. There's not any written rules that *I* know of, you might want to ask a more experienced writer, but I don't think there are. Maybe read some more fanfics to get yourself a bearing on the writing styles, and create your own voice? So much to do! I'm starting a fic myself. So I know what you're dealing with! Good luck!